Several braking or locking techniques are used at present:
the locking wire technique. This technique, which is much used in the aeronautical field, does not guarantee the mechanical holding together of the assembly. This locking system is more moral than mechanical. PA1 locking techniques using a plastic washer set into a nut, using an elastic or deformed nut, using an elastic washer or using friction. These systems either limit the assembly clearance between the thread of the nipple and the nut, or they increase the torque necessary for loosening. They do not therefore totally guarantee against the risk of the installation becoming loosened during its use. PA1 a support member having a mounting portion, a lock-support portion and first engagement means; PA1 a locking member having a bearing portion which is movably supported by said lock-support portion of said support member between a locking position and a withdrawn or release position, a coupling formation, and second engagement means, wherein, at least in said locking position of the locking member, said first and second engagement means are mutually engaged so as to prevent rotation of said locking member with respect to said support member; and PA1 a return means mounted operatively between said locking member and said support member for biassing said locking member into said locking position. PA1 a first engagement means which is made stationary with respect to the first element; PA1 a locking member having coupling means and a second engagement means and which is axially slidable with respect to the first element between a locking position in which said coupling means is capable of coupling for common rotation with said second element whereas said first and second engagement means are in mutual engagement preventing rotation of said locking member with respect to said first element, and a release position in which at least one of said coupling means and said second engagement means is disengaged from said second element and from said first engagement means respectively; PA1 a return means biassing said locking member into said locking position, PA1 a tubular body provided with an internal threading; PA1 a threaded shaft threadingly engaged in said internal threading; PA1 a counternut threadingly engaged on said threaded shaft; PA1 first engagement means which are integral with said tubular body; PA1 an annular locking member having a coupling formation and second engagement means, said locking member being axially movable with respect to said tubular body between a locking position in which said first and second engagement means are in mutual engagement and in which said coupling formation is angularly coupled with said counternut when said counternut is positioned adjacent said tubular body, and a release position in which at least one of said coupling formation and said second engagement means are disengaged from said counternut and from said first engagement means respectively; PA1 return means biassing said locking member into said locking position. PA1 a collar belt terminated by two end-blocks at least one of which is tubular; PA1 a threaded bolt extending through said tubular end-block and engaging said other end-block, thereby to be operable to draw said end-blocks towards each other and correspondingly tighten said collar-belt; PA1 a tool grip element operatively connected to said threaded bolt; PA1 first engagement means which are integral with said tubular end-block; PA1 an annular locking member having a coupling formation and second engagement means, said annular locking member being axially movable with respect to said tubular end-block between a locking position in which said coupling formation engages said tool grip element thereby to be angularly fast therewith and in which said first and second engagement means are in mutual engagement, and a release position in which at least one of said coupling formation and said second engagement means are disengaged from said tool-grip element and from said first engagement means respectively; PA1 return means biassing said locking member into said locking position.
Most of these techniques cannot be used again after a dismantling.
According to another locking technique known from U.S. Pat. No. 5,083,819, for pipe connections, locking tabs fixed to the nipple resiliently engage the nut. This technique is expensive.
Furthermore, a locking device is known from FR-A-917 287 in which one of the pipes has a thread made beyond splines on which a locking member is slidably mounted. The locking member is biassed by a spring into a locking position in which, in use, said locking member immobilizes the nut carried by the other pipe and engaging said thread. This device is not compatible with the standard couplings since it requires the provision of splines between the thread and the actual piping. The total length of the coupling is modified by this and the total cost is very high. The device according to U.S. Pat. No. 5,188,398 is of the same type but has the additional disadvantage that the splines of the locking member must be strong because they also serve to transmit the tightening torque.
According to U.S. Pat. No. 4,655,482, the nut and the hexagonal conformation of the threaded pipe end are used to rotationally immobilize locking parts which fit over them. The hexagonal conformations of the nut and of the threaded pipe are therefore no longer accessible for the tightening operation. To overcome this, the locking parts have external hexagonal conformations. The radial dimension is increased by the locking parts, which must furthermore transmit the tightening torque.
Thus, most of the known locking devices require an extensive re-designing work of the basic structure comprising the elements to be locked, and that the locking device be an integral part thereof.